Fusobacterium nucleatum promotes bladder cancer progression and immune escape by activating the IL22/STAT3/PD-L1 signaling cascade

Objective: This study investigates the mechanism by which Fusobacterium nucleatum (Fn) promotes bladder Cancer (BC) progression and immune escape through the interleukin 22 (IL22)/signal transducer and activator of transcription 3 (STAT3)/programmed death-ligand 1 (PD-L1) cascade signaling.

Methods: Fecal samples from BC patients (n = 73) and healthy controls (n = 39) were analyzed for Fn abundance using qRT-PCR. IL-22, p-STAT3, STAT3, and PD-L1 levels were determined by qRT-PCR and western blot. The in vitro cultured human BC cell line (T24) were co-cultured with Fn, followed by CCK-8, colony formation, and Transwell assays to assess cell viability, proliferation, and invasion and migration, respectively. A co-culture system of T24 and CD8-positive T lymphocytes (CD8⁺ T) cells was established. Immune responses were assessed by determining tumor necrosis factor alpha (TNF-α), interferon gamma (INF-γ), granzyme B (GZMB), and pore-forming protein (Perforin) levels in supernatants. In vivo studies using a BC mouse model examined tumor progression and immune markers through flow cytometry, focusing on CD8⁺ T cells and regulatory T cell (Treg) populations. Immunohistochemical assay was conducted to measure ki67 levels in tumor tissues.

Results: Fn levels were significantly elevated in BC patients' feces. Fn treatment enhanced Cancer cell viability, proliferation, invasion, and migration. Fn activated the IL22/STAT3/PD-L1 pathway and showed positive correlations with these markers in BC tissues. In the co-culture system, Fn reduced CD8⁺ T cell function and increased Treg proportions in tumor tissues. The in vivo experiments confirmed that Fn promoted IL22/STAT3/PD-L1 expression, altered immune cell ratios, and increased ki67 expression levels.

Conclusion: Fn promotes the IL22/STAT3/PD-L1 cascade signaling, thereby facilitating in vivo progression and immune evasion of BC.

Bladder cancer; Fusobacterium nucleatum; Immune evasion; Interleukin 22; Programmed death-ligand 1; Signal transducer and activator of transcription.